Abstract: Malignant tumors still remains the disease seriously threatening human being's health. Metastasis and recurrence are the two hang ups for cancer treatment, but the mechanism is yet unclear. The theory of the cancer stem cell gives a newexplanation that a small group of tumor cells with selfrenewal and indefinite potency exist in the tumors, which are regarded as the sources in metastasis and recurrence of the tumors. So far, the tumor stem cells have already been separated and determined in leukemia, multiple myeloma, breast cancer, CNS tumor and lung cancer. The evidence for existence of tumor stem cells have also been found in gastric and liver cancer. The human beings have new cognitions for metastasis and recurrence of tumor with proposal and verification of the theory of the cancer stem cell, which will produce a significant influence on treatment of tumor and prevention for the metastasis and recurrence.